Affinity (law)

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In law and in cultural anthropology, affinity, as distinguished from consanguinity (blood relationship), is the kinship relationship that is created or exists between two or more people as a result of someone's marriage. It is the relationship which each party to a marriage has to the relations of the other partner to the marriage; but does not cover the marital relationship of the parties to the marriage themselves. Though laws vary considerably, affinity does not always cease with the death of one of the marriage partners through whom affinity is traced, nor with the divorce of the marriage partners. In addition to kinship by marriage, "affinity" can sometimes also include kinship by adoption and step relationship.

Under the law, such relatives by marriage are known as affines. More commonly, they are known as in-laws or family-in-law, as affinity is usually signified by adding "-in-law" to a degree of kinship.[n 1]

In law, affinity may be relevant in relation to prohibitions on incestuous sexual relations and in relation to whether particular couples are prohibited from marrying. Which relationships are prohibited vary from country to country, and have varied over time. In some countries, especially in the past, the prohibited relationships were based on religious laws. (See, for example, Affinity under canon law.)


In South Africa, sexual relations are prohibited within the first degree of affinity, that is, where one person is the direct ancestor or descendant of the spouse of the other person.[1]

Brazilian law, by the Article 1521 of the Civil Code, also extends the invalidity of marriage between parents and children to grandparents and grandchildren or any other sort of ascendant-descendant relationship (both consanguineous and adoptive), parents-in-law and children-in-law even after the divorce of the earlier couple, as well as to stepparents and stepchildren, and former husbands or wives to an adoptive parent who did this unilaterally (regarded as an equivalent, in families formed by adoption, to stepparents and stepchildren); and extends the invalidity of marriage between siblings to biological cousin-siblings.[2][3]

In Hawaii, sexual penetration and marriage is prohibited within close degrees affinity and is punishable by up to 5 years.[4]

In Michigan, sexual contact between persons related "by blood or affinity to the third degree" are chargeable as criminal sexual conduct in the 4th degree and punishable by a 2-year sentence or a fine of up to $500 or both.[5]

In New Jersey, sexual contact is prohibited when the actor is "related to the victim by blood or affinity to the 3rd degree" and the victim is at least 16 but less than 18 years old.[6]

See also[edit]


  1. ^ This is standard for the closest degrees of kinship—father-in-law, daughter-in-law, &c.—but is frequently omitted in the case of more extended relations. As uncle and aunt are frequently used to refer indifferently to friends of the family, the terms may be used without specifying whether the person is a cognate or affine. Similarly, the spouse of a cousin may not be called a relation at all or may be referenced as a "cousin by marriage".


  1. ^ Criminal Law (Sexual Offences and Related Matters) Amendment Act, 2007, s. 12.
  2. ^ "Mundo do Direito, da Hist贸ria, da M煤sica e da Literatura".
  3. ^ Direito Brasil – Marriage (in Portuguese)
  4. ^ Haw. Rev. Stat. § 707-741 and 706-660
  5. ^ MCLS §
  6. ^ N.J.S.A. 2C:14-2(b-c) and N.J.S.A. 2C:14-3 in NEW JERSEY, Rape, Abuse & Incest National Network